1. Field of the Invention
The present invention relates to a method of and an apparatus for immunologically analyzing a measuring object in the field of clinical testing, biochemical sample measurement, drug quality control or the like.
2. Description of the Background Art
Immunological analysis methods employing antigen-antibody reaction include fluorescent immunoassay and luminescent immunoassay. These methods are adapted to competitively react an antigen, which is labeled with a fluorescent material or a chemiluminescent material, with a measuring object antigen with respect to an antibody for measuring fluorescence or luminescence from the label of an antigen-antibody reacted immunocomplex, thereby quantitatively analyzing the measuring object material.
A method of adding an antigen or an antibody of a measuring object material to an antibody or an antigen and measuring light absorption or scattering by an immunocomplex which is formed by antigen-antibody reaction thereby making quantitative analysis is known as an optical measuring method utilizing neither fluorescence nor luminescence. Quantitative analysis methods employing light scattering include turbidimetry and nephelometry, which are adapted to measure transmitted light attenuated by absorption and scattering and to measure intensity of scattered light respectively.
The method employing light scattering measures Rayleigh or Mie scattering, in response to sizes of particles as measured. No wavelength shifting is caused in Rayleigh or Mie scattering, and scattering intensity at an excitation light wavelength is measured.
On the other hand, surface-sensitized Raman spectrometry is employed as a method of measuring vibration spectra of molecules. This method utilizes such a phenomenon that strong Raman scattering is caused when a material is adsorbed on the surface of a noble metal electrode or colloid of gold or silver (refer to "Bunseki", 1993, pp. 577-585, for example). Protein, bilirubin and the like are studied through such surface-sensitized Raman spectrometry. It is known that vibration spectra are enhanced to 10.sup.7 to 10.sup.8 times upon occurrence of surface-sensitized Raman scattering, to allow measurement of high sensitivity.
However, fluorescent or luminescent immunoassay requires complicated chemical treatment for labelling an antigen or an antibody with a fluorescent or chemiluminescent material. In general, further, such immunoassay is heterogeneous immunoassay, which requires a B-F separating operation for separating an antigen-antibody reacted immunocomplex (B) from a nonreacted antigen (F) and a washing operation, leading to increase in number of analysis steps.
On the other hand, the method utilizing light scattering, which is homogeneous immunoassay, can be simply carried out with requirement for neither B-F separation nor washing. However, the method employing Rayleigh or Mie scattering has a problem of low detection sensitivity and low measurement accuracy as to a low concentration material.
Although study of the surface-sensitized Raman spectrometry is made on protein and bilirubin, there has been made no report on measurement of surface-sensitized Raman scattering in relation to an immunocomplex which is formed through antigen-antibody reaction.